PRINCETON — If Vanessa Marcotte had not fought so fiercely in the last moments of her life, a suspect in her killing could have driven straight past the State Police detective in Worcester last month unrecognized.

But the 27-year-old Marcotte, whose battered and burned body was discovered in the woods near her mother’s home in Princeton last August, left detectives with her killer’s DNA, which was on her hands, and they used it to create a physical profile.

On Saturday, Worcester District Attorney Joseph D. Early Jr. said he believes that authorities have found their man: 31-year-old Angelo Colon-Ortiz of Worcester. In mid-March, Colon-Ortiz happened to drive past a state trooper, who recognized him from the physical profile. The trooper scribbled Colon-Ortiz’s license plate on his hand. A DNA swab matched.

“We got him,” Early said at an afternoon press conference as dozens gathered cheered and applauded. “There is also one other person I’d like to thank in this case, and that would be Vanessa Marcotte. It was through her determined fight and her efforts that we obtained the DNA of her killer.”

Colon-Ortiz has only been charged with aggravated assault and battery and assault with intent to rape, but Early said he expected a murder charge shortly. So far, investigators have not been able to turn up any criminal history on Colon-Ortiz, officials said.

Marcotte’s family released a statement late Saturday night, thanking investigators and the entire community for their help in identifying and finding the suspect.

“After eight long months, we’re able to take the first step toward justice for Vanessa,” they wrote. “She was a beautiful, intelligent, and generous young woman whose passion for giving back to the community will always be remembered.”

David L. Ryan/Globe Staff

Vanessa Marcotte

Marcotte loved running, hiking, and volunteering, and called the beaches in Brewster her “happy place.”

She had landed her “dream job” working for Google and was living in New York City when she came home to Princeton in August to visit her family.

But after she went out for a run on Aug. 7, she never returned. Her family called police, who discovered her body in the woods off a two-lane road, a half-mile from her mother’s home. A law enforcement official has said her body had been burned.

Investigators used the DNA sample found on her body, combined with witness statements from people who might have seen the killer, to create a physical description of a “person of interest,” which they announced in February.

The man was believed to be Hispanic with an athletic build, light to medium skin, average height, and about 30 years old, and to drive a dark-colored SUV.

Investigators fielded more than 1,300 tips, but it took the serendipitous sighting to break the case. One day last month, officials said, Trooper Robert Parr, who is assigned to the detective unit and was working the Marcotte case, saw a man who fit the physical description drive past him in Worcester, in a dark SUV.

Parr couldn’t find any paper, so he jotted the license on his hand, went to the correlated address, and left his card, officials said. He went back the next day with another trooper and talked to Colon-Ortiz, who agreed to a DNA swab.

The results came back on Friday. Investigators took Colon-Ortiz in and arrested him early Saturday morning.

In Princeton, residents were relieved at news of the arrest. The rural town in Central Massachusetts had changed since Marcotte’s killing. It thrust the town into the national media, and put a spotlight on dangers faced by runners, especially women.

“Since this happened, I haven’t seen anyone out alone,” said Jenna Masiello, 23, who has lived in town her entire life but whose parents no longer let her walk or run outside by herself. “Without him being caught, people just didn’t know. Could he be living up the street?”

Megan Weeks, a runner in the town who has been training for Monday’s Boston Marathon, said she feels like she’s regained a sense of freedom.

As her training intensified and her runs became longer, finding a willing running buddy became more difficult. She said she continued to run alone, but she had to change her routine: She texted her husband every mile, and he would frequently drive around town to check on her while she ran.

“You kind of start living differently and accepting that this is a new way of life,” she said.

Weeks said the arrest, which came as a surprise to many community members, immediately eased the anxiety in town.

“You feel like you can walk down the street and not be looking over your shoulder,” she said.

Though Marcotte’s family did not speak to reporters, her father and uncle attended the press conference along with other townspeople. At the end, once more, the crowd applauded.